In vivo and in vitro generation of a new altered HLA phenotype in melanoma-tumour-cell variants expressing a single HLA-class-I allele.
A new HLA-class-I altered phenotype is described in melanoma. This phenotype is the result of a combination of HLA-B-locus down-regulation and HLA-haplotype loss. The alteration was found in 2 melanoma cell lines generated from 2 patients; one was derived from an in vivo lesion (FM37) and the other was obtained after in vitro immunoselection (R22.2). The R22.2 cell line was isolated from FM55P, a cell line derived from a primary melanoma, after in vitro treatment with a heterologous HLA-A2-restricted cytotoxic-T-lymphocyte (CTL) clone. Two additional cell lines from patient 55 were obtained from 2 s.c. metastases (FM55M1 and FM55M2). Iso-electric focusing and flow-cytometric studies showed a significant reduction in the expression of both HLA-B alleles in all cell lines studied. The expression of HLA-B-locus products recovered completely after IFN-gamma treatment of FM55P, M1 and M2. In contrast, FM37 and R22.2 tumour cells showed an additional HLA defect: the absence of one HLA haplotype. Simple tandem-repeat polymorphism markers spanning chromosome 6 showed that DNA from the 2 samples (FM37 and R22.2) showed loss of heterozygosity (LOH). In both cases, homozygosity was observed on 6p, which maps the HLA region, the final consequence being a tumour cell that expressed a single HLA-class-I allele (HLA-A3 and HLA-A1 respectively). FM37 cells may thus reflect the in vivo counterpart of resistance to lysis by HLA-A2-restricted tumour-infiltrating lymphocytes.
Real
L M
LM
Departamento de Análisis Clínicos, Hospital Universitario Virgen de las Nieves, Universidad de Granada, Spain.
Jimenez
P
P
Cantón
J
J
Kirkin
A
A
García
A
A
Abril
E
E
Zeuthen
J
J
Ruiz-Cabello
F
F
Garrido
F
F
D000483:Alleles; D005805:Genes, MHC Class I; D015789:HLA-A2 Antigen / Q000235:genetics; D015235:HLA-B Antigens / Q000235:genetics; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D008545:Melanoma / Q000235:genetics / Q000276:immunology*; D010641:Phenotype; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D014407:Tumor Cells, Cultured
D015789:HLA-A2 Antigen; D015235:HLA-B Antigens; D007371:Interferon-gamma